Air suspensions utilize air springs to provide desired output characteristics, such as ride comfort, maintaining vehicle height and vehicle performance for example. One known active air suspension uses an air spring assembly that includes a primary airbag mounted around a piston airbag such that the piston airbag provides a rolling surface for the primary airbag. A change in piston airbag volume changes an effective piston area of the primary airbag. A relatively small change in the effective piston area provides a change in a spring rate of the air spring assembly. The pressures in the piston airbag and the primary airbag are selectively controlled to provide infinite variation in spring rates. The smaller volume of the piston airbag relative to the larger volume of the primary airbag permits rapid pressure and volume changes to enable active suspension control.
Typically, there is one air spring located at each corner of the vehicle such that vehicle ride height can be adjusted by increasing or decreasing pressure within the air spring assembly. Vehicles equipped with suspension systems that have multiple airbags at each corner have difficulty adjusting vehicle ride height in a smooth and repeatable manner. A main function of the primary airbag is to bear the vehicle weight and control the vehicle height at each corner. The main function of the piston airbag is to change the spring rate or load at each corner. An effect of change of the volume or pressure of the piston airbag is a corresponding change in ride height. This often results in the vehicle changing direction one or more times during a single height or spring rate change request, resulting in a vehicle oscillation. Thus, there is a need to provide a ride height control for an active air suspension with a dual air spring configuration where changes in ride height are accomplished smoothly without multiple changes in direction.